1. Field of the Invention
The present invention relates to an engine control system that controls the operating condition of an engine mounted in an automobile etc.
2. Description of the Related Art
Conventionally, as illustrated in for example Laid-open Japanese Patent Publication No. Hei 7-332132, in an engine control system arranged so as to control the idling speed of the engine by adjusting the rate of intake passing through the engine intake bypass passage, rise in engine speed was curbed by lowering the torque generated immediately after start-up by lowering the bypass intake rate for a predetermined time by a predetermined amount in response to engine temperature, when a predetermined engine speed had been reached, after start-up of engine operation.
Also, the engine control system as described in the above publication is constructed such that, when the engine temperature drops below a predetermined value, the rate of intake that is admitted to the engine combustion chamber is increased by inhibiting the aforesaid control for lowering the bypass intake rate, in order to maintain an optimum condition in regard to fuel consumption.
However, in the idling condition of the engine, basically, the rate of intake is small, so when, as mentioned above, the engine temperature is low, even if control is exercised so as to increase somewhat the rate of intake admitted into the combustion chamber of the engine, there is the problem that no particularly large effect can regard to accelerating vaporization and atomization of the fuel by the air current can be expected; rather, since the intake air negative pressure is small, vaporization and atomization of the fuel adhering to the intake passage are poor and combustion characteristics deteriorate. It should be noted that, when heavy gasoline of high density is employed as fuel, there is the problem that, if the intake and negative pressure is lowered by increasing the intake rate as described above, fuel combustion characteristics are severely impaired.
In view of the above, an object of the present invention is to provide an engine control system wherein deterioration of combustion characteristics when engine temperature is low can be effectively prevented.
In order to achieve the above object, an engine control system, according to the invention, comprises temperature discrimination means that identify engine temperature and intake pressure control means that, when said temperature discrimination means identifies low engine temperature after engine start-up, executes control to increase the intake negative pressure with respect to the normal level until the temperature of an intake passage has risen to at or above a predetermined value.
With the above construction, when the temperature discrimination means identifies low engine temperature after engine start-up, the intake pressure control means executes control whereby the intake negative pressure is made larger than normally, until the temperature of the intake passage has risen to at or above the predetermined temperature, thereby promoting vaporization and atomization of fuel adhering to the intake passage, so good combustion characteristics of the fuel can be ensured.
These and other objects, features and advantages of the present invention will become more apparent upon reading of the following detailed description along with the accompanied drawings.